The field of RFID systems has evolved over the past years from systems developed in relatively large packages (size of a cigarette package) containing battery powered transmission/receiving circuitry or transceiver, such as the identification system disclosed in U.S. Pat. No. 4,274,083, to passive systems (the size of a credit card) in which the transceiver receives its power from the base station or interrogator, such as the identification system disclosed in U.S. Pat. No. 4,654,658.
Although a low-cost RFID system having a battery powered transceiver allows for greater distance between the interrogator and the transceiver units, the physical size of the transceiver unit has pushed the industry towards the passive transceiver technology as disclosed in U.S. Pat. Nos. 4,654,658 and 4,730,188. However, the limit in RF communication distance between transceiver and interrogator in low-cost passive systems is in the 2 foot or less range if reasonable accuracy of information collected is to be achieved and low power, low-cost interrogators are to be used.
U.S. Pat. No. 4,724,427 discloses a passive RFID transceiver as well as a hybrid battery operated version which addresses both types of RFID systems.
The memory used in RFID systems depends on the type of system used wherein, most passive systems use a programmable read only memory (PROM) of some sort that will retain its programmed data even when power is disrupted or removed while a battery backed system may use any memory type, including random access memory (RAM), that requires a continuous power source to retain programmed data.
Though an RFID system may vary in transceiver type, the memory used and circuitry configuration, all RFID systems have a common characteristic: that being a receive/send antenna(s) component. The present invention discloses the development of a three-dimensional spherical antenna pattern that is constructed from elements arranged in a two-dimensional plane, a method for switching to various antenna elements and passive recharging of secondary battery cell(s) powering RFID transceiver tags, each of which will allow improved operation of compatible RFID systems that will readily be recognized by one skilled in the art in accordance with the present invention described herein. Also, all U.S. Patents cited herein are hereby incorporated by reference.